Indicator for pneumatic tires



Feb. 16, 1954 V- O-S--TIEN HAL INDICATOR FOR PNEUMATIC TIRES CHAR Les 0.130 NoN o. sLET Fld June 22, 1950 VER Patented F el). 16, 1954 OFFICE 2,669,617 INDICATOR FOR PNEUMATIC TIRES Vernon 0. Sletten and Charles C. Bowman, Havre, Mont.

Application June 22, 1950, Serial No. 169,663 Claims. (Cl. 20o-61.25)

The present invention relates to an indicator' for pneumatic tires, and more particularly has reference to an indicator' assembly adapted to be installed within the valve stem of a tire for giving a visual or an audible signal to the driver of the Vehicle when the tire air pressure reaches a predetermined point.

Viewing the invention broadly, it comprises loeating a spring-controlled longitudinally slidebe member Within the valve stern, which member connected with a circuit for a signal disposed within the vehicle such as a warning lamp on the dashboard, the slidable member normally1 maintaining the circuit to the lamp open when the tire pressure is above a predetermined point, but adapted to be moved to a circuit-making position to light the signal lamp when the tenw sion of the spring means cooperating therewith is greater than the tire pressure.

The device is relatively simple in structural detail as well as operation and can be readily incorporated in `conventional tires with little modication of the tire structure.

An important object of the present invention is to provide a Warning signal for indicating to the driver of the vehicle that the tire pressure has fallen below a safe minimum pressure wherein the signal is instantly eiected when the predetermined tire pressure has been reached.

Yet a further object of our invention is to provide a signalling device for pneumatic tires for indicating to the vehicle driver that the pressure has fallen to a predetermined pressure, which can be manufactured at a comparatively W cost and which by virtue of the relatively few essential parts presents no maintenance or repair problems.

With the foregoing and other objects in view, the invention consists in the details of construction, and in the arrangement and combination of parts to be hereinafter more fully set forth and claimed.

In describing the invention in detail, reference will be had to the accompanying drawings forming a part of this application wherein like characters denote corresponding parts in the several views, and in which:

Figure l is a fragmental view in side elevation of a motor vehicle equipped with the indicator of the present invention.

Figure 2 is a vertical sectional View of the valve stem of a tire equipped with the present signalling device.

As clearly-illustrated in Figure 2, we have indicated the conventional tire I0, Il is a valve `conductor #lll with slip ring stem externally threaded, as shown at i 2, to receive a closure cap I3, and le deno es generally the control assembly for a signal lamp I5 located preferably on the dashboard of the vehicle.

The assembly 54 comprises a metallic conductor sleeve l5 which snugly lits within the valve stem l l, and the upper end of the sleeve l5 is externally threaded, as shown at Il, to engage internal threads lll provided on the upper end of the valve stem il, and the lower end of the sleeve it is formed with an internal annular ilange is constituting a fixed contact which Will later be more fully described. A metallic guide member 2t is disposed within the sleeve l5 and the upper end thereof is threaded, as indicated at 2 l, to engage corresponding threads 22 formed in the upper end of the sleeve it. A piston 23 is disposed below the guide member 2! and 'the external diameter of the piston is slightly less than the internal diameter oi the sleeve it so that the piston may have sliding movement longitudinally within the sleeve. The piston is formed of a suitable non-conductive material, and the upper face of the piston supports an annular gasket 24. The piston is formed with a vertical bore 25, the lower end of which merges with a conical recess 25 in the body of the piston, and both the bore 25 and the recess 25 are lined with a suitable conductive material 2l forming a movable contact.

A helical spring 28 is located within the guide member 26, and the upper end of the spring bears against an annular flange 29 integrally formed with the guide member, while the lower end of the spring bears against the gasket Erl and the head of the piston The spring tends to urge the piston 23 downwardly, the downward movement of the piston being limited or arrested by the annular iiange le fern ed on the lower end oi the metal sleeve le.

A metal guide tube 3S is mounted within the guide member 2li and an air release rod 3i provided With a Valve 32 at the lower end thereof is disposed within the tube Sil. A spring 33 is supported at the lower end oi the pist-cn 23 to restrain the downward movement of the rod 3i' and the valve head 32. A conductor 3f! is atu tached to the upper end of the tube 35 and is connected through a lead 35 with slip ring 313 located within the hub of the wheel. 3l is connected with the lamp l5, while lead 3e connects the lamp with battery B which is as shown at 39. The cap i3 is connected by a it! which, in turn,

grounded, as shown at 2. Thus, lead 35 and conductor 46 are the conductor wires for the movable and the xed contacts, respectively.

The tube 3B is connected with the metal line 21 by a conducting wire 43, and opening e in the upper Wall of the cap I3 is insulated as indicated at 45.

As is apparent from Figure 2, the inflation path of the tire is from the upper end of such view to the tire, the path extending through the space between the ange of guide member 20 and the guide tube 3i), through the spring chamber within the guide member, and into the axial opening in metal liner 25 in block 23 and the frustoconical seat at the outlet end of such opening and with which the complemental end 32 of rod 3| cooperates, the path then extending through the axial opening in flange i9; since spring 33 overlies the latter opening to limit the movement of rod 3i, the truste-conical form of the liner opening outlet and the head of rod 3! provides the spread of the path so as to provide open communication in the path on opposite sides of spring 33 to insure free passage of the inating air, while the pressure in the inated tube has free access to hold the rod head to its seat, with the shape of the seat and inner side of the head insuring extended contact therebetween to prevent as far as possible leakage of air from the tube in the return direction, the relatively large dimensions of the outer face of the head affording ample area Vfor making the tube pressure effective to hold the head tightly to its seat. While the open lower end of tube 3B is thus exposed to such path, it does not affect the inating action since the tube is immovable and the closed end of the conductor 3d prevents any escape of air in the reverse direction.

Another advantage of the iniiation path arranged in this way is the fact that it places practically the outer face of piston 23 exposed to the iniating pressure, thus adding this pressure to that of spring 28 to move the piston to its position of contact between the metal lining 25 and iiange i9, the position which completes the circuit through the light, thus assuring that the light will remain lit until the counter-pressure is able to overcome the pressure of the spring plus the inating pressure; since the spring in this position has its lowered pressure value-due to its expansion, this addition of the inflating pressure to maintain the circuit-closing position does not make an excessive pressure, but permits the building up of the tube pressure to the desired maximum value. As will be understood when during inilation, the opposing pressure values approach equilibrii the gradual increase in pressure values Within the tube nally overpowers the opposing pressure with the result that head 32 seats, and thus places the piston or block under the pressure within the tube, moving it away from flange i9 and breaking the circuit, this movement oi the piston continuing until it again reaches contact with guide member 2S, the power of spring 2S growing through the piston movement, to prevent too rapid movement of the piston as the seated head closes iurther admission of iniiatingair, and gradually sets the assembly and completes the cycle and sets the assembly to meet the conditions which serve to produce the succeeding cycle of operation.

Another advantage of the assembly is provided by the location and eect produced by air release rod or element 3i and its head 32 within "the inating path as above explained. rEhe head in' cooperation with liner 25 produces a valve eiect within the path between the path entrance and the inner tube, with the head constantly exposed to the pressure within the tube, so that the valve eect is present at all times excepting during actual infiating action through the paththe inflating pressure necessarily exceeding the pressure within the tube to permit ination, and hence, during periods when it is being applied will unseat the head to permit air introduction to the tube, the head instantly moving to seated position upon cessation of iniiating, and remaining seated until the next inflating action is provided.

The rod or element 3l has no contact relation with spring 28 at any time the stem or rod being isolated from the spring by guide tube 3i); hence, the spring has no effect on the valve, except to change its position in the path through the movement of the piston or block 23, such movement not affecting the seated condition of the valveeven in the circuit closing position of the piston and its liner in contact with internal ange i9 does not affect this condition. Hence, the valve eiect remains active to tend to separate the path into a pair of sections, one of which extends from the entrance of the path to such valve with the other section directly communicating with the interior of the inner tube, the result being that the valve is always subject to the pressure within the inner tube due to this particular section, and Without regard to the pressure conditions within the other section, excepting during actual inating periods-there could be excessive slow leakage action within the latter section of the path and form a diierential in pressure on opposite sides or" the valve and in the two sections, the valve or seated head tending to reduce leakage conditions in the inner tube section of the path to a minimum. Because of this, there is less likelihood of damage arising through failure to respond immediately to the lighted signal, excepting in cases of blowout conditions in the tire.

The operation of the signal may be summarized as follows:

When the tire has been inated to the desired pressure, the piston 23 will compress the spring 28 and the gasket 24 will be forced into tight engagement with the lower end of the guide member 29 and at the same time the valve head 32 will fit tightly against the walls of theY conical recess 25, thereby providing a tight seal to prevent the escape or" air from the tube. However, when the air pressure falls below the pressure of the spring 2S, the spring will force the piston 23 downwardly until the metal liner 2l engages the flange i9 on the sleeves I6. Since the sleeve I6 is metal and is in direct contact with the cap I3, the sleeve is grounded through conductor 48, slip ring i and the ground i2 and a circuit is completed through liner El, conducting wire 43, tube Se, conductor 3d, lead 35, slip ring 36 to the light through the lead 38 to the battery B. Hence, the driver of the Vehicle is given an instantaneous visual signal that the tire pressure has fallen below the desired pressure and should be checked.

rEhe invention is not to be coniined to any strict conformity with the showing in the drawing, but may be changed or modiiied so long as such changes or modications mark no material departure from the salient features of the invention as expressed in the appended claims.

We claim:

l. in a pressure responsive switch for a tire denation signal, a conductive sleeve located within the tire valve stem forming a fixed contact,

a movable contact disposed within the sleeve and normally maintained out of circuit closure with the sleeve by the tire pressure, spring means cooperating with said movable contact tending to urge the movable contact into engagement with an internal flange within the sleeve, conducting Wires for the fixed and movable contacts and complemental means on the sleeve and the valve stem to retain the sleeve and movable contact within the valve stem, the inflation path for the tire extending internally of the sleeve and through the movable contact and through an axial opening of the internal iange of the sleeve.

2. A pressure responsive switch as claimed in claim 1 wherein sleeve located within the valve stem is provided with an internal annular iiange` at the lower end thereof and the movable contact includes a block of non-conductive material slidably mounted within the sleeve, and a metal Contact of annular type carried by the block is adapted to engage the annular flange of the sleeve to complete the circuit, said metal contact interior forming the ination path section carried by the movable contact.

3. A pressure responsive switch as claimed in claim 2 wherein the said block is provided with a bore extending therethrough, and a metal liner in said bore, the metal liner constituting the block contact and being adapted to engage the annular flange of the sleeve to close the signalling circuit.

4. A pressure responsive switch as claimed in claim 3 wherein the lower end of the bore merges with a frusto-conical recess and an air release rod projects through the bore and terminates in a frusto-conical valve head, the taper of the valve head coinciding with the taper of the recess, said valve head constituting a controlling element in the tire inflation path.

5. A pressure responsive switch as claimed in claim 1 wherein a guide member is iixedly secured within the sleeve above the movable contact for supporting the spring means, said guide member forming a stop to limit the movement of the movable contact in one direction.

VERNON -O. SLETTEN. CHARLES C. BOWMAN.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,183,486 Pardue May 16, 1916 1,410,297 Harman Mar. 21, 1922 1,975,639 Greene Oct. 2, 1934 2,445,959 Luper July 27, 1948 

